Protective coating for motionpicture films



Aug. 26, 1952 R. H. REDFIELD 2,608,127

PROTECTIVE COATING FOR MOTION-PICTURE FILMS Filed May 2o, 194e PatentedAug. 26, 1952 UNITED STATES PATENT orrice PROTECTIVE COATING FOR MOTION-PICTURE FILMS Robert H. Redfield, Oak Park, Ill.

A 'Application May 20, 1948, Serial No. 30,787 (c1. rss-19.5)

Claims,

This invention relates generally Yto an improved protective coating formotion picture film and to an improved method and apparatus for applyingthe coating to the film.

Protective coatings have been applied to motion picture lms for manyyears, the purpose ofthe coatings being in` most cases to protect theemulsion on the surface of the positive film against abrasion orscratching whichA ,is encountered when .thefilm is run through aprojector. A great many different kinds of coatings have been used, butnone of them have proved wholly satisfactory. These coatings may bedivided into two general types: (l)v those which are harder than theemulsion. and therefore resistant to abrasion but which have nolubricating properties and (2) those which also serve as a lubricant.This latter type of coating usually comprises a layer of wax applied tothel film on the emulsion side or on both sides. Al-

though the invention is described herein in con-` nection with a coatingof the latter 'type itis not limited to such coatings for its principlesmay be readily applied to the former type.

One of the major difiiculties experienced with coatings heretofore inuse is that such coatings are by necessity quite thin and transparent tolight, and, consequently, it is diiiicult to tell by inspection whetherYa film has been coated lor not and if coated what the condition of thecoating is, i. e., whether the coating has been scratched and what isthe thickness of the coating remaining.

O-ne object of this invention is lto provide a protective coating havinga tell-tale indicator portion by which it is possible to tell at aglance whether or not the given film has been coated. o

Another object of this invention is to provide an` indicator stripewhich extends the entire length of the film and which may be readilyexamined to determine the condition of the protecy tive coating of thefilm.

Another object is to provide a film coating over the emulsion aswellasthe perforated edge portion of the film and anfindicator coatingwhich overlaps that portion of the film coating which covers theperforated edge portion.

Another object is to provide an indicator in the form of a coloredstripe on the edge of the film which wears simultaneously with theprotective coating but which is visible so that the relative thicknessof the lm coating may be estimated by observing the depth of color ofthe indicator.

A further object is to provide a colored indicator stripe upon whichscratches or abrasion 2 will be readily apparent and which may be usedon either colored or black and white films whether originals, masterprints, duplicate negatives, work prints, or positive prints.

.A further object is to provide an indicator stripe so located as not tointerfere with pictures projected or with the sound being produced inthe event that the sound film is coated.

A further object is to provide an indicator stripe located on that partof the lm subject to the greatest amount of wear.

Another object is to provide a film coating and an indicator coatingwhich overlays the film coating so that wear is most likely to occur onthe indicator coating.

A further object is to provide a novel method and apparatus for applyingthe coating material and indicator stripe to.-motion picture lm.

Other and additional objects of this invention will'y present themselvesto those familiar with the vart on reading :the following specificationin conjunction with the drawing and the appended claims.

In the drawing:

Fig. 1 is a schematic view showing the manner in which the protectivecoating and the indicator stripe of the invention are applied to a reelof motion picture lm;

Fig. 2 is an enlarged cross section of a strip of film coated accordingto this invention;

Fig. 3 is a view showing a strip of sound film after coating;

Fig. 4 is an enlarged view of a portion of a strip of silent film;

Fig. 5 is an enlarged View showing the stripeapplying rollerarrangement;

Fig. 6 is a vertical section taken on line E-Ei of Fig. 5; and L Fig. 7is a view of one of the feed rollers which locates the film during itspassage over the striped line roller.

The preferred method of applying the coating of this invention to astrip of film I@ is shown in Fig. 1. The lm IG is fed from a reel Ilover a feed roller l2 and over the surface of an absorbent roller I3.The roller I3 rotates through a reservoir M containing the protectivecoating solution, and as the film I0 passes over the roller i3 a layerof the solution is deposited thereon. From the roller I3 the film passesover a series of drying rollers i5 solvent evaporating from the coatingsolution and causing the coating to harden or solidify. From the dryingrollers l5 the film passes over another feed roller IS and over astripeapplying roller II of absorbent material such as felt. A reservoirI8 containing the indicator solution is mounted below the roller ilsimilarly to the coating solution reservoir I4 and the roller Il rotatesthrough the solution depositing a stripe on the lm ID. After passingover a second set of drying rollers 26, the film I is rolled on to asecond reel I2 and the process is complete.

The preferred coating solution comprises a hard wax such as beeswax,carnauba or paraine dissolved in a solvent such as carbon tetrachloride,lacquer thinner, xylene, toluene, or trichloroethylene. Inasmuch as thesolvent is evaporated during the process, any substance which willdissolve the wax and not the film and which does not react chemicallywith either may be employed. The wax solution preferably has aconcentration of approximately one ounceV of wax per gallon of solvent.

The indicator stripe solution is preferably made so as to be identicalwith the coating solution except that an oil soluble dye is dissolvedtherein. For this purpose oil soluble aniline dyes have proved verysatisfactory. In practice the simplest method of making the indicatorsolution is'to take` a portion of the coatingA solution and add'v thedesiredv amount of dye to it, theV amount ofv dye being dependent on thedepth of color desired. BlackY and white are considered to be colors.

When other coatings than wax areto be. employed, the process is exactlytheA same except that. a. suitable solvent for theV coating materialmust be used and a dye oricolor` which is soluble in the solution ischosen.

After thefilm It has been coated itappears as shown in Figs. 2, 3, and4. As shown in Fig. 2

the emulsion 22 is completelycovered by. the Y protective coating. 23,the coating 23 formingY a layer over the surface of the emulsion. 22vand. filling those spots from which the emulsion has.

been dissolved during the process of development with the result thatthe surface of the film is substantially fiat. In the exampleillustrated, it will be noted that the emulsion does not cover thesprocket holes 24 andthat consequently the coating 23 is not quite ashigh on that sideV of.

the lm I0 as it is over. the remaining part. yThe indicator. coating25.1ieson top of the protective coating 23 at the edge ofthe film I0..Thus the indicator coating is in the form of a colored stripe along theside of the film I0 and extends inwardly to approximately the mid-pointof the sprocket holes 24. It will be noted that vthe heights. of the topof the indicatorcoating-andtlietop of the protective coating above thefilm surfaceare substantially identical.

In Fig. 2 the thickness of the protective'coating 23, and the emulsion`22, and. the indicator stripe 25 have been 'exaggerated for the processof illustration. Actually these coatingslare approximately 1/1000 or oooof-4 an inch in thickness when conventional 16 mm. or 35mm. lm isprocessed. f

16 mm. sound nlm is usually provided with sprocket openings on one sideonly,-the other side of the lm being occupied by the sound track 26. Onsuch film the emulsion is likely to be applied to either side of thenlm, some lms being run through the projector with the emulsion sideadjacent the light source and others' with'the emulsion away fromthelight source. Consequently, it is necessary to employ an apparatuswhich will coat the emulsion'regardless of which side of the film itlies on 'and which .shaft 21 is driven in the opposite direction fromthe film I0 so that the surface of the roller I'I wipes over the surfaceof the film I0. A pair of Iguide rollers 30 and 3| are mounted on theshaft 21 but are free to rotate independently thereof. Actually theserollers 30 and 3| rotate in the direction of nlm movement and do nottherefore exert a traction on the lm. An adjustable pressure roller 29is provided and serves to prevent excessive quantities of the solutionbeing deposited on the film I 0.

The feed rollers I 6 havethree flanges 32 thereon so that two tracks forthe nlm. I6 result. When the film It is in. the leftvhand track, asshown in Fig. 7, it passes overthe roller 30 in Fig. 5, the right` handedge ofithefilm coming into contact with the dye roller Il. When .thelfilm I0 is shifted to theright hand track ofthe rollers as shown in Fig.'7, itpassesover theright roller-to accomplish the same. result.

In order to insure that thefilm I0 will always remain in contact withthe. dyeroller I'I, a conventional frictiondrag brake (not shown) ispro-- vided on the roller/I6. This brake exertsaslight.

retarding effect on the roller I6 which thereby exerts a' slight tensionon the .'rllm I0. .No brake is provided on thefopposite rfeedroller I'Sawhich is otherwise identical Vwith the roller I6.

From the Vforegoingit will be seen that anoveli improved protectivecoating` for lm has been.

provided-which makes it possible to readily observe the condition of thecoating. Thus a nlm owner may decide, by merely-.examining theA in.

dicator stripe, whether afilmr should be recoated eliminating theneedforV recoating lms at intervals,Y whether they need it or not just to beon the safe side, and insuring that-films in need:

of recoating will bedetectedas-soon as the need existsi l Variouschanges or modifications' in the-coating,- apparatus, and process suchas thef appli-l cationofthe indicator 'stripe before-the coating.

is appliedk so that the coating overlays the stripe .and otherswhichwill occur to those familiar with the art may bevmade without departingfrom the spirit of this invention-whose scope isY dened by the'followingclaims.

What is claimed is: Y

-1. A motion picture lm comprising a strip of transparent exiblematerial having a plurality of spaced sprocket holes along one edgeportion, a developed emulsion surface covering a -major portion of thestrip, a transparent invisible protective coating covering saidIdevelopedV emulsion surface and said edge portion, and a colored wearindicator stripe along said edge portion of saidfilm overlaying theprotective coating and' having substantially the same wearing qualitiesas If the sprocket holes 24 areon theother side of the film, it is runover the. other side of the feed accede? said protective coa-ting,whereby the relative wear of the transparent coating may beinferentially determined by visual inspection of the degree of wear onthe colored stripe, the stripe overlaying the protective c-oating andbeing disposed at that portion of the iilm subjected to greatest wear.

2. A motion picture film comprising a strip of transparent flexiblematerial having a plurality of spaced sprocket holes along one edgeportion, a developed emulsion surface covering a major portion of `thestrip not including the edg-e portion having said sprocket holes, atransparent invisible protective coating covering said developedemulsion surface and said edge portion, and a colored wear indicatorstripe along the sprocket por-tion of said film overlaying theprotective coating and having substantially the same wearing qualitiesas said protective coating, whereby the relative wear of thetransp-arent coating may be inferentially determined by visualinspection of the degree of wear of the colored stripe.

3, A strip of developed sound motion picture iilm having a central areadevoted to the picture frames, a side area having a sound track thereonand another side area containing sprocket hole means for conducting theiilm through a projector, a transparent protective coating over thecentral area and the sound track area of the lm, and a colored stripealong the other side area for indicating the degree of wear of theinvisible transparent coating, said stripe being a coating containing adye and having subs-tantially the same Wearing qualities as saidtransparent coat, whereby the degree of wear of the transparent coatingmay be inferentially determined by visual inspection o-f the coloredcoating.

i4. A strip of developed motion picture lm having a central area devotedto the picture frames, a side area containing sprocket hole means forconducting the film through a projector, a transparent protectivecoating of wax over the central area of the iilm, and a colored stripealong the side where greatest wear occurs for indicating the degree ofwear of the invisible transparent coating, said stripe being a Waxcoating containing a dye and having substantially the saine wearingqualities as said transparent coating, whereby the relative wear of thetransparent coating may be inferentially determined by visual inspectionof the degree of wear of the colored coating.

5. A strip of developed motion picture film `having a central areadevoted to the picture frames, a side area containing sprocket holemeans for conducting the lm through a projector, a transparentprotective coating over the 4central area of the lm, and a coloredstripe along said side area where greatest w-ear occurs for indicatingthe degree of wear of the invisible transparent coating, said stripebeing a coating containing a dye and having substantially the samewearing qualities .as said transparent coating, whereby the relativewear of the transparent coating may be inferentially determined byvisual inspection of the degree of Wear of the colored coating.

ROBERT H. REDFIELD.

REFERENCES CITED The following references are of record in the fgle ci"this patent:

UNITED STATES PATENTS Number Name Date 1,203,548 Trivelli Oct. 3-1, 1916`1,226,555 Grosvenor May 22, 191,7 1,453,920 Clark May 1, 1923 1,548,951Malone Aug. 11, 1925 i1,787,8'25 Jones Jan. 6, 193'1 1,849,232 HickmanMar. 1'5, 1932 1,892,473 Rodde Dec. 27, 1932 2,059,829 Ward Nov. 3, 19362,331,575 lSimons Oct. 12, 1943 2,331,746` Talbot Oct. 12, 19432,376,\1841y Rand May l5, 1945 FOREIGN PATENTS Number Country Date'240,532' Great Britain Oct. 1, 1925

